1. Field of the Invention
The application relates to a method utilized in a wireless communication system and related communication device, and more particularly, to a method of handling a communication operation and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of the universal mobile telecommunication system (UMTS) for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (COMP) transmissions/reception, uplink (UL) multiple-input multiple-output (MIMO), etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
The CA is introduced to the LTE-A system by which more than one carrier (e.g., component carriers, serving cells) can be aggregated to achieve a wide-band transmission. The CA increases bandwidth flexibility by aggregating the carriers. When a UE is configured with the CA, the UE has the ability to receive and/or transmit packets via one or multiple carriers to increase throughput.
Different from the LTE/LTE-A system operating in a frequency-division duplexing (FDD) mode (or simply FDD system), directions of subframes of a frequency band in the LTE/LTE-A system operating in a time-division duplexing (TDD) mode (or simply TDD system) may be different. That is, the subframes in the same frequency band are divided into UL subframes, downlink (DL) subframes and special subframes according to the UL/DL configuration specified in the 3GPP standard.
FIG. 1 is a table 102 of the UL/DL configuration with subframes and corresponding directions. In FIG. 1, 7 UL/DL configurations are shown, wherein each of the UL/DL configurations indicates a set of directions (i.e., transmission directions) for 10 subframes, respectively. Each subframe is indicated with respective subframe number (i.e., subframe index) in FIG. 1. In detail, “U” represents that the subframe is a UL subframe where UL data is transmitted, and “D” represents that the subframe is a DL subframe where DL data is transmitted. “S” represents that the subframe is a special subframe where control information and maybe data (according to the special subframe configuration) is transmitted, and the special subframe can also be seen as the DL subframe in the prior art. Note that the eNB may configure a UL/DL configuration to a UE via a higher layer signaling (e.g., System Information Block Type 1 (SIB1)) or a physical layer signaling (e.g., DL control information (DCI)).
According to the 3GPP standards which have been developed, the UE cannot operate in the TDD mode and the FDD mode at the same time. That is, the UE can only perform a transmission/reception via TDD carrier(s), or can only perform the transmission/reception via FDD carrier(s). Bandwidth efficiency and flexibility are limited, when the UE can only use a specific type of carriers. Thus, it is expected that the UE may perform the transmission/reception via the TDD carrier(s) and the FDD carrier(s) jointly, i.e., TDD-FDD joint operation is expected. However, rules according to which the TDD carrier(s) and FDD carrier(s) are used are different. The UE cannot simply perform the transmission/reception via the TDD carrier(s) and the FDD carrier(s) at the same time.
Thus, realization of a communication operation (e.g., TDD-FDD joint operation) is an important problem to be solved.